Field-modulating angular position measuring devices may be based on an inductive, magnetic or capacitive measuring principle and are used, for example, in rotary encoders for determining the angular position of two machine parts that are rotatable with respect to each other.
As a scanning device in field-modulating inductive angular position measuring devices, excitation coils and receiver coils are often mounted in the form of circuit traces on a shared circuit board, which is permanently connected, for example, to a stator of a rotary encoder. Arranged across from this circuit board is another board, on which as a measuring graduation electrically conductive areas are mounted at periodic intervals, and which is connected to the rotor of the rotary encoder in a rotatably fixed manner. If an electric excitation field is applied on the excitation coils, output signals as a function of the angular position are generated in the receiving coils during the relative rotation between rotor and stator. These output signals are then processed further in evaluation electronics. The components of such evaluation electronics are often accommodated on an additional circuit board. The circuit board having the excitation and receiver coils and the circuit board having the evaluation electronics are often connected to each other via flex conductors and plug-in connections.
European Published Patent Application No. 1 126 248 describes a method for determining the scanning distance, which is suited to calibrate exactly the scanning distance for the calibrating operation prior to the actual measuring operation. The method and the angular position measuring device are believed to have the disadvantage that in the actual measuring operation of the angular position measuring device the scanning distance can be determined only in a comparatively imprecise manner.